I've added some new updates to the post "third-party iPhone apps I actually use," including MightyDocs, which displays Google docs offline (now with spreadsheet support); SayWho, a free voice-activated dialer; Amazon, which lets you shop and compare prices and even experiment with looking up products via iPhone photographs (it worked for me with a pretty bad photo of an obscure book); and Twitterific, which even in ad-supported free mode is overtaking my earlier favorite Twitter client, Twinkle.